Hyundai HX220 NL EPFC Fault Code 108-2: Technical Guide

What is Hyundai HX220 NL EPFC Fault Code 108-2?

Fault Code 108-2 indicates an intermittent signal problem with the Engine Coolant Temperature (ECT) Sensor circuit. This diagnostic trouble code (DTC) specifically means the Engine Control Module (ECM) has detected an erratic or unstable voltage signal from the coolant temperature sensor, typically caused by poor electrical connections or sensor degradation.

The ECT sensor plays a critical role in the HX220 NL's engine management system by monitoring coolant temperature and sending voltage signals to the ECM. This data directly affects fuel injection timing, idle speed control, and engine warm-up cycles. An intermittent signal (the "-2" suffix) means the fault isn't constant but occurs sporadically, making diagnosis more challenging than a complete sensor failure.

For used excavators, this code is particularly common due to connector corrosion and wiring harness deterioration from years of exposure to engine heat cycles and vibration.

Common Symptoms

• Erratic engine idle speed that fluctuates unexpectedly, especially during warm-up
• Hard starting when the engine is cold or after sitting overnight
• Check engine light illuminates intermittently rather than staying constant
• Poor fuel economy and black exhaust smoke during operation
• Engine fan running constantly at high speed regardless of actual coolant temperature

Potential Causes

The most frequent causes of Code 108-2 on used HX220 NL excavators include:

• Corroded or loose electrical connectors at the ECT sensor or ECM harness connection points
• Damaged wiring harness with intermittent shorts or opens, particularly where the harness routes near the engine block
• Failing ECT sensor with internal resistance breakdown causing intermittent signal dropout
• Contaminated sensor threads with coolant leak residue or corrosion affecting ground connection
• ECM connector pin corrosion from moisture intrusion in older machines
• Aftermarket sensor incompatibility if the sensor was previously replaced with non-OEM parts

How to Troubleshoot and Fix Code 108-2

Step 1: Visual Inspection Begin by inspecting the ECT sensor connector located on the engine block near the thermostat housing. Disconnect the connector and examine both male and female pins for green corrosion, bent pins, or moisture. Check the wiring harness for abrasion points where it contacts the engine or frame, common wear areas on used machines.

Step 2: Electrical Testing Using a digital multimeter, check the sensor resistance. With the engine cold, resistance should read approximately 2,000-3,000 ohms at 68°F (20°C). As the engine warms, resistance should decrease smoothly to around 200-300 ohms at operating temperature. Erratic readings indicate sensor replacement is needed. Also test harness continuity from sensor to ECM connector (pins should show less than 5 ohms resistance).

Step 3: Connector Repair and Sensor Replacement Clean all connectors with electrical contact cleaner and apply dielectric grease to prevent future corrosion—critical for used equipment. If testing confirms sensor failure, replace with an OEM Hyundai ECT sensor (part number specific to HX220 NL EPFC). Torque the new sensor to 15-20 Nm and ensure proper thread sealant is used.

Step 4: Clear Codes and Road Test After repairs, use Hi-MATE diagnostic software (Hyundai's factory tool) or a compatible scanner to clear fault codes. Operate the excavator through multiple heat cycles while monitoring live ECT sensor data to confirm stable voltage signals (typically 0.5-4.5V range depending on temperature).

Professional Tip for Used Excavators: Before replacing the sensor, wiggle the harness connector while monitoring live data—if the signal drops out, the issue is connector-related rather than sensor failure, saving unnecessary parts replacement.

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Disclaimer: This guide provides general troubleshooting information for Code 108-2. Always consult the official Hyundai service manual for your specific machine serial number and software version. If you're unfamiliar with electrical diagnostics or lack proper tools, contact a certified Hyundai heavy equipment technician to prevent misdiagnosis or further damage.